Nightmare continues for citrus growers

Citrus greening disease is being addressed on four fronts simultaneously: research, regulatory, agricultural and consumer.

Rod Santa Ana, Texas A&M AgriLife | Jun 17, 2013

“Citrus trees are crashing,” said Ricke Kress, president of Southern Gardens, a large citrus grower and juice producer in southern Florida who spoke recently at the North American Agricultural Biotechnology Council’s 25th annual conference.

“We’re experiencing a 15 percent loss of fruit that’s falling off our trees,” he said. “These trees have been stressed by adverse weather conditions, which was exacerbated by citrus greening disease. By dropping fruit, trees are doing what they have to do to survive, but is this going to be a trend? We have to wait and see, but this could lead to a supply crisis.”

Kress addressed the potential of disease-resistant transgenic citrus trees, developed by Dr. Erik Mirkov, a Texas A&M AgriLife Research plant pathologist in Weslaco, to overcome greening, an incurable bacterial disease that clogs a tree’s vascular system. Fruit fails to mature — thus, the name citrus greening — and trees eventually die.

“It’s not like testing a new variety of corn that can be planted, tested and go forward,” he said. “It takes time, years, for citrus trees to mature and produce fruit. So, to reach a point of solution, we’re working on several programs concurrently.”

Kress said the issue is being addressed on four fronts simultaneously: research, regulatory, agricultural and consumer.

“Research to find a solution,” he said. “In regulatory, we’re preparing proposals to get the solution approved. Agriculture? We need to grow the trees. And consumers? We need to make sure consumers understand that the technology being developed is safe. If we don’t have consumer confidence, it doesn’t matter what we come up with.”

The conference, “Biotechnology and North American Specialty Crops: Linking Research, Regulation and Stakeholders,” was held June 4-6.

The three-day event gathered stakeholders to discuss effective means of moving fruit and vegetable crops improved through biotechnology from laboratories and research field plots to consumers, according to Dr. Bill McCutchen, executive associate director of AgriLife Research in College Station.

“Citrus is just one example,” McCutchen said. “Through the use of biotechnology, scientists have developed improved varieties of apples, pineapples, potatoes, squash and other specialty crops with disease resistance and other favorable traits.

“Fruits and vegetables are the next wave of transgenic food crops that will provide a way to help producers keep pace with world population growth,” he said.

Stakeholders, including scientific researchers, government officials and industry leaders such as Kress, discussed the role of biotechnology and regulatory policy in improving agriculture, McCutchen said.

By moving genetic material from spinach, Mirkov developed citrus trees that show potential resistance to citrus greening and are now being field tested at Southern Gardens.

“We’ve set up field trials since 2009, and trials continue with new variations of transgenic trees,” Kress said. “We’re letting Mother Nature tell us how well those trees work. But that takes time. And depending on variables, some trees survive, some don’t. But that’s science.”

While there is no clear-cut solution to citrus greening yet, there is hope, Kress said.

Solution is close

“We’re getting close. It looks promising. It’s positive, and we’re making progress, but we’re still working on a solution.”

In his talk, Kress provided an overview of citrus greening’s effect on the Florida citrus industry.

“It spread very quickly,” he said. “Greening was first confirmed in Florida in 2005 and in three years had been found in every citrus-producing county of the state. There are no formal surveys being taken today, but the consensus is that every citrus grove in Florida has greening to some degree. No one can say they don’t have greening.”

Southern Gardens Citrus has lost some 700,000 trees to the disease, Kress said.

“We’ve lost 25 to 28 percent of our total acreage since the disease was detected,” he said. “It’s a tough one. We remove trees when infection is found, but not all growers follow the same practice. They try nutritional programs and other efforts to maintain and extend the life of the tree. But by doing so, are we increasing the rate of infection to other trees? There are more questions than answers at this point.”

The disease is spread from tree to tree by the Asian citrus psyllid, an insect that growers should assume is in their fields, Kress said.

“Some growers spray insecticides only after they find psyllids,” he said. “That’s too late. Growers should put their spray program in place to take care of it.”